This application claims the priority of Korean Patent Application No. 2002-74122, filed on Nov. 26, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a field effect transistor (FET) using a compound semiconductor, such as a metal-semiconductor field effect transistor (MESFET) or a high electron mobility transistor (HEMT), and a method of manufacturing the same.
2. Description of the Related Art
Recently, devices, such as an MESFET and a HEMT which are compound semiconductor microwave devices, are widely utilized to manufacture ultrahigh frequency integrated circuits (ICs). The devices have excellent noise characteristics in a radio frequency band and are essentially utilized to manufacture low noise amplifiers. The FETs used as a basic device for an IC employ a multi-level metallization (MLM) structure. A narrow and long interconnection is formed for such an MLM structure. In particular, an FET for an amplifier having an excellent radio frequency characteristic forms a T-shaped gate electrode, so as to perform a high-speed operation and have a high gain and a low noise characteristic, thereby reducing the length of a gate electrode.
A conventional FET having a T-shaped gate electrode uses a silicon nitride layer, so as to protect the surface of a compound semiconductor substrate. In this case, the silicon nitride layer is interposed between the T-shaped gate electrode and a source electrode. In this structure, parasitic capacitance exists between a head portion of the T-shaped gate electrode and the source electrode. As such, signal delay and electrical cross-talk occur, causing the operating speed of a device to restrict and reduce a cut-off frequency fT. Thus, in order to solve the problem, a material having a lower dielectric constant needs to be used as an insulating layer.